Hotbed hot tub

I’d hate to learn English as a second language simply because of weird stuff like ‘hotbed’ being one word and ‘hot tub’ being two words. Where’s the logic in that?

Hotbed:  Metalworking.
an area having rails or rolls on which rolled pieces are laid to cool.

hot·bed, n., v., -bed·ded, -bed·ding.
1.    a bottomless, boxlike, usually glass-covered structure and the bed of earth it covers, heated typically by fermenting manure or electrical cables, for growing plants out of season.
2.    a place or environment favoring rapid growth or spread, esp. of something disliked or unwanted: a hotbed of disease.
3.    Slang. a bed shared by two or more persons in shifts, each sleeping in it for or at a designated time and then vacating it for the next occupant.
4.    Slang. to share a bed in shifts, so that it is always occupied.
[1620–30; HOT + BED]

Hot tub: a wooden tub, usually large enough to accommodate several persons, that is filled with hot aerated water and often equipped with a thermostat and whirlpool: used for recreation or physical therapy and often placed out of doors, as on a porch.

People may place plants in a hotbed, whereas people plant themselves in a hot tub. How confusing is that to someone learning English.

A hot tub can also be a hotbed of disease if not properly maintained.

I made the words ‘hotbed’ and ‘hot tub’ while working on my next word puzzle ebook. It is a 6-letter word ebook and I was making as many 6-letter words as I could from the phrase “ODD ABOUT THE”. (I found 16 six-letter words. Try it yourself and see how many you find using each letter only once.)